This invention relates to an endless belt, to an endless belt photoconductor, an endless belt and roller structure, and to an image forming apparatus.
In the field of image forming apparatuses such as copying machines and printing machines, there are increasing needs for color-formation, high speed image formation, compact apparatuses and high durability. The use of a large diameter photoconductor drum may satisfy the needs for high speed image formation and high durability but the apparatus becomes unavoidably large in size. The use of an endless belt photoconductor, the shape of which can be easily changed by use of rollers, can solve the above problem.
The endless belt photoconductor generally has a photoconductor layer provided on a support made of an electrically conductive material such as a conductive polymer or a metal. Because of dimensional stability, a metal support is preferably used for an endless belt photoconductor for high speed image formation. An endless belt is supported by a plurality of rollers and adapted to run by rotation of drive roller or rollers. Since each of the rollers for supporting the endless belt is generally not perfectly uniform in diameter throughout the axial length thereof, in sphericity of the cross-sectional shape thereof and in straightness of the axis thereof, the endless belt is apt to laterally move or meander during running. A large lateral movement of the belt may result in disengagement thereof from the rollers and breakage thereof. Further, even when the amplitude of the lateral movement is small, image quality is deteriorated especially when the endless belt photoconductor is used for full color image formation in which a color image is produced by superimposing yellow, cyan and magenta images.
To cope with the problems of lateral movement, there are proposals in which guides are provided on an inside surface of the belt along opposite side edges. The guides are disposed such that at least one of the side walls is in engagement with a side end of at least one of the rollers by which the endless belt is supported. For example, Japanese Laid Open Publication No. S59-230950 proposes an endless belt having guides prepared by applying a hot melt adhesive to an inside surface of the belt along opposite side edges. The melt is then cooled and solidified. Because the guides are apt to deform during the cooling step, however, the thus prepared guides cannot prevent lateral movement of the belt for a long period of operation. Japanese Laid Open Publication No. H04-190280 discloses an endless belt having rubber guides having a specific thickness and a rubber hardness. When the belt is driven at a high linear speed, however, the guides are apt to deform and separate from the belt.
There is also proposed a different type of means for preventing lateral movement of the endless belt, in which a pair of ribs are provided on an inside surface of the belt along opposite side edges. The ribs are disposed for fitting engagement with grooves provided on outer periphery of drive rollers by which the endless belt is supported or for engagement with sloped portions provided at both side ends of drive rollers by which the endless belt is supported. For example, in Japanese Laid Open Publication No. 2000-131998, the inside surface of each of the ribs which is in contact with and bonded to the inner surface of the belt is roughened to have an average surface roughness Ra of at least 0.3 xcexcm to improve adhesion between the rib and the belt. It has been found, however, that when the known endless belt is operated at a high linear speed of, for example, 80 mm/sec or more, there often occurs delamination or separation of the rib from the belt. Japanese Laid Open Publication No. 2000-132001 discloses an endless belt having a pair of ribs bonded to an inner surface of the belt along a side end of the belt. The outer surface of each of the ribs at which the rib is brought into contact with rollers is roughened to have an average surface roughness Ra of at least 0.3 xcexcm to decrease friction therebetween. It has been found, however, that when the known endless belt is operated at a high linear speed of, for example, 80 mm/sec or more, there often occurs lateral movement of the belt. The above endless belt and roller mechanism is also disadvantageous in that it needs the formation of grooves or inclined portions on the rollers.
It is an object of the present invention to provide an endless belt which has overcome the above problems of the conventional endless belts.
Another object of the present invention is to provide an endless belt of the above-mentioned type which can be driven at a high running speed without lateral movement.
It is a further object of the present invention to provide an endless belt photoconductor suited for a high speed, full color image forming system which is embodied into a compact, high durability apparatus and which can produce full color images free of printing defects attributed to printed color misregistrations attributed to printed color misregistrations in superposed or closely adjacent images.
In accomplishing the foregoing objects, there is provided in accordance with the present invention an endless belt comprising an endless body having opposite side edges and an interior surface, and a pair of spaced apart parallel guides bonded through an adhesive layer to the interior surface of the endless body at positions adjacent to the side edges thereof and extending longitudinally along the side edges, wherein each of the guides is made of an elastic material and has an inside surface which constitutes an interface between the guide and the adhesive layer and which provides I(S) of 0.5-13.0, wherein I(S) is given by the following equations:                                           I            ⁡                          (              S              )                                =                                    (                              1                N                            )                        ⁢                                          ∑                                  n                  =                  0                                                  N                  -                  1                                            ⁢                              {                                  S                  ⁡                                      (                                          n                                                                        N                          ·                          Δ                                                ⁢                                                  xe2x80x83                                                ⁢                        t                                                              )                                                  }                                                                                              S            ⁡                          (                              n                                                      N                    ·                    Δ                                    ⁢                                      xe2x80x83                                    ⁢                  t                                            )                                =                                    1              N                        ·                                          "LeftBracketingBar"                                  X                  ⁡                                      (                                          n                                                                        N                          ·                          Δ                                                ⁢                                                  xe2x80x83                                                ⁢                        t                                                              )                                                  "RightBracketingBar"                            2                                                      X      ⁡              (                  n                                    N              ·              Δ                        ⁢                          xe2x80x83                        ⁢            t                          )              =                  ∑                  m          =          0                          N          -          1                    ⁢                        x          ⁡                      (                                          m                ·                Δ                            ⁢                              xe2x80x83                            ⁢              t                        )                          ⁢                  exp          ⁡                      (                                          -                ⅈ2                            ⁢                              xe2x80x83                            ⁢                              π                ·                                  n                                                            N                      ·                      Δ                                        ⁢                                          xe2x80x83                                        ⁢                    t                                                  ·                m                ·                Δ                            ⁢                              xe2x80x83                            ⁢              t                        )                              
wherein
N is a number of samples obtained from a sectional curve of the inside surface of the guide and is 2p where p is an integer,
xcex94t is a sampling interval, in xcexcm, at which the N-number of the samples are sampled in the longitudinal direction of the guide, the sectional curve being obtained by measuring a profile of the inside surface of the guide through a preset length Nxc2x7xcex94t,
x(t) is a height of the sectional curve, in xcexcm, of a sample at a position t in the preset length, and n and m are integers.
The present invention also provides an endless belt comprising an endless body having opposite side edges and an interior surface, and a pair of spaced apart parallel guides bonded through adhesive layers to the interior surface of said endless body at positions adjacent to said side edges thereof and extending longitudinally along said side edges, wherein each of said guides is made of an elastic material and has an inside surface which constitutes an interface between said guide and said adhesive layer and which has Rz of 3-16 xcexcm, wherein Rz is an average surface roughness at ten points of a sectional curve obtained by measuring a profile of the inside surface of said guide in the longitudinal direction of said guide.
The present invention also provides an endless belt and roller structure comprising a plurality of rollers, and one of the above-described endless belts supported by the rollers, so that by rotation of the rollers, the endless belt runs in the longitudinal direction of the guides with a side surface of each of the guides being in contact with a side surface of each of said rollers.
The present invention further provides an image forming apparatus comprising the above endless belt and roller structure.
The present inventors have investigated causes for lowering of image quality when increasing the linear velocity of an endless belt photoconductor to which guides are bonded and found that adhesion between the guides and the belt is one of the important factor with respect to lateral movement of the endless belt photoconductor. It has been also found that the lateral movement can be prevented by controlling surface conditions of the inside surfaces of the guides constituting the interface between the guides and the belt.
The average surface roughness Ra can properly represent magnitude of average unevenness of a sectional curve only when the waves of the sectional curve have similar amplitudes. In actual, however, various waves having various amplitudes and various wavelengths are superimposed one over the other in a sectional curve of a roughened surface. Since minute waves superimposed on waves with large amplitudes are cancelled in calculating Ra and thus are not reflected in Ra at all, surface conditions defined by Ra cannot solve the problem of lateral movement of an endless belt.
The present inventors have investigated a relationship between a sectional curve of a guide bonded to an endless belt photoconductor and the image quality obtained using the photoconductor and have found that waves having relatively small amplitudes as well as waves having large amplitudes largely influence the adhesion of the guide to the belt and, thus, the image quality. The present inventors has also found that a power spectrum obtained by discrete Fourier transformation of a sectional curve of a surface of a guide which provides an interface between the guide and an endless belt represent powers of waves constituting the sectional curve and that it is a total of the powers of all of these waves that properly represent the surface conditions of the guide that give suitable adhesion between the guide and the belt.
The present invention also provides an endless belt comprising an endless body having opposite side edges and an interior surface, and a pair of spaced apart parallel guides fixedly secured to the interior surface of the endless body at positions adjacent to the side edges thereof and extending longitudinally along the side edges, wherein each of the guides is made of an elastic material and has an outside surface providing Ixe2x80x2(S) of 0.5-10.0, wherein Ixe2x80x2(S) is given by the following equations:                                                         I              xe2x80x2                        ⁡                          (              S              )                                =                                    (                              1                                  N                  xe2x80x2                                            )                        ⁢                                          ∑                                  n                  =                  0                                                                      N                    xe2x80x2                                    -                  1                                            ⁢                              {                                  S                  ⁡                                      (                                          n                                                                                                    N                            xe2x80x2                                                    ·                          Δ                                                ⁢                                                  xe2x80x83                                                ⁢                                                  t                          xe2x80x2                                                                                      )                                                  }                                                                                              S            ⁡                          (                              n                                                                            N                      xe2x80x2                                        ·                    Δ                                    ⁢                                      xe2x80x83                                    ⁢                                      t                    xe2x80x2                                                              )                                =                                    1                              N                xe2x80x2                                      ·                                          "LeftBracketingBar"                                  X                  ⁡                                      (                                          n                                                                                                    N                            xe2x80x2                                                    ·                          Δ                                                ⁢                                                  xe2x80x83                                                ⁢                                                  t                          xe2x80x2                                                                                      )                                                  "RightBracketingBar"                            2                                                      X      ⁡              (                  n                                                    N                xe2x80x2                            ·              Δ                        ⁢                          xe2x80x83                        ⁢                          t              xe2x80x2                                      )              =                  ∑                  m          =          0                          N          -          1                    ⁢                                    x            xe2x80x2                    ⁡                      (                                          m                ·                Δ                            ⁢                              xe2x80x83                            ⁢                              t                xe2x80x2                                      )                          ⁢                  exp          ⁡                      (                                          -                ⅈ2                            ⁢                              xe2x80x83                            ⁢                              π                ·                                  n                                                                                    N                                                  xe2x80x2                          .                                                                    ·                      Δ                                        ⁢                                          xe2x80x83                                        ⁢                                          t                      xe2x80x2                                                                      ·                m                ·                Δ                            ⁢                              xe2x80x83                            ⁢                              t                xe2x80x2                                      )                              
wherein
Nxe2x80x2 is a number of Samples obtained from a sectional curve of the outside surface of the guide and is 2p where p is an integer,
xcex94txe2x80x2 is a sampling interval, in xcexcm, at which the Nxe2x80x2-number of the samples are sampled in the longitudinal direction of the guide, the sectional curve being obtained by measuring a profile of the outside surface of the guide through a preset length Nxe2x80x2xc2x7xcex94txe2x80x2,
xxe2x80x2(txe2x80x2) is a height of the sectional curve, in xcexcm, of a sample at a position txe2x80x2 in the preset length, and
n and m are integers.
In a further aspect, the present invention provides an endless belt comprising an endless body having opposite side edges and an interior surface, and a pair of spaced apart parallel guides fixedly secured to the interior surface of said endless body at positions adjacent to said side edges thereof and extending longitudinally along said side edges, wherein each of said guides is made of an elastic material and has an outside surface having Rzxe2x80x2 of 2-20 xcexcm, wherein Rzxe2x80x2 is an average surface roughness at ten points of a sectional curve obtained by measuring a profile of the outside surface of said guide in the longitudinal direction of said guide.
The present invention also provides an endless belt and roller structure comprising a plurality of rollers, and one of the above-described endless belts supported by the rollers, so that by rotation of the rollers, the endless belt runs in the longitudinal direction of the guides with a side surface of at least one of the guides being in contact with a side surface of at least one of said rollers.
The present invention further provides an image forming apparatus comprising the above endless belt and roller structure.
It has also been found that the lateral movement of the endless belt may be prevented by controlling surface conditions of the outside surfaces of the guides, even though the outside surface of each of the guides are not brought into contact with the drive and other rollers by which the endless belt is supported. It is the side wall of at least one of the guides that is brought into contact with a side end surface of at least one of the rollers, especially at least one of drive rollers. It has been found that a large compressive stress is applied to the guides at their outer surface regions, when the guides are passed through and flexed by drive and other rollers. It has also been found that such a stress may be reduced by controlling surface conditions of the outside surfaces of the guides.
It has been found that a power spectrum obtained by discrete Fourier transformation of a sectional curve of an outside surface of a guide which is not brought into contact with rollers represent powers of waves constituting the sectional curve and that it is a total of the powers of all of these waves that properly represent the surface conditions of the guide that reduce mechanical stress applied to the guide upon flexed by drive an other rollers. dr
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention which follows, when considered in the light of the accompanying drawings, in which:
FIG. 1 is a sectional view schematically illustrating one embodiment of an endless tape photoconductor according to the present invention;
FIG. 2 is a perspective view schematically illustrating one embodiment of an endless tape and roller structure according to the present invention;
FIG. 3 is a sectional view schematically illustrating another embodiment of an endless tape photoconductor according to the present invention;
FIG. 4 is a schematic sectional view showing an image forming apparatus according to the present invention; and
FIG. 5 is a schematic illustration of a sectional curve of a surface of a guide.